Frequency scanning arrangement



. M. SILVER FREQUENCY SCANNING ARRANGEMENT April 26, 1949.

Filed July 11, 1945 a I E W w O M... W M c INVENTOR. M/yWT/N 5/; v5?

Patented Apr. 26, 1949 FREQUENCY SCANNING ARRANGEMENT Martin Silver, Bronx, N. Y., assignor to Federal Telephone and Radi 0 Corporation, New York,

N. Y, a corporation of Delaware Application July 11, 1945, Serial No. 604,360

3 Claims.

The present invention relates to radio communication and more particularly to communication apparatus incorporating means for continuously scanning one or more given bands of frequencies both for receiving and transmitting purposes.

In numerous applications of the radio communication art it is often desirable to cover by continuous scanning a given spectrum of frequencies. Such is the case for instance when distant transmitters are to be located the frequencies of which are unknown except for the general spectrum, and which may have to be replied to on their own frequency. A known application of this type is that of jamming a hostile transmitter in times of war.

It is accordingly an object of this invention to provide automatically operable means for transmitting or receiving circuits which will scan continuously and repetitiously one or more frequency bands.

It is another object of the invention to provide a multiple band frequency scanning means.

It is still another object to provide means for tuning an inductive circuit such as to effect the scanning. of a given frequency band.

A further object is to provide a rotatable tuning disc for inductive circuits constructed such as to provide for a variation in the inductive circuit associated therewith in a linear relationship with res-pecttothe rotation thereof.

In accordance with the invention a number of inductive tuning circuits for a receiver or transmitter may be provided in the form of split induction coils wherein a given set of coils may be put into the main circuit for covering a given band of frequencies.

Other and additional coils of the same type may be provided on a rotatable turret which may be placed in contact with the main circuit if a shift in the frequency band is desired. Intermediate the two halves of each of the frequency band tuning coils there is posi tioned for rotary displacement with respect thereto a tuning disc comprised of an insulator mem ber which has mounted thereon preferably a metallic foil such as copper shaped to provide a predetermined frequency scanning relationship in respect to the rotation of the disc. The foil is preferably shaped to vary the mutual inductance of the two coil portions, which are in the main circuit, from a given maximum to a given minimum for each rotation of the disc.

These and other objects and features of my invention will become more apparent upon consideration of the following detailed description of an embodiment of the invention to be read in connection with the accompanying drawings in which:

Fig. l is a schematic diagram of a representative circuit incorporating the frequency scanning means of the invention;

Fig. 2 is a schematic representation of a tuning disc and associated circuit tuning coils;

Fig. 3 is a schematic view in section on the line 3-3 of the tuning arrangement of Fig. 2; and

Fig. 4 is a graph showing the variation of irequency with time of the signal output of the circuit of Fig. 1.

Referring to Fig. 1, a receiver circuit I is shown in schematic form comprising an antenna circuit 2 which includes an inductance 3 and a ground connection 4. The main receiving circuit 5 of the receiver I is coupled to the antenna inductance 3 by means of a tuned circuit 6 which may be comprised of a plurality of sets of inductive tuning coils l, 8 and 9 and an adjustable condenser l0. Each set of coils 'l, 8 and 9 comprises two halves as at la and lb and may be connected to the main circuit 5 by means of contacts l l and 12. The switching operation of the three sets of coils which cover different and successive frequency band portions may be accomplished by means of a rotatable turret as will be described in detail hereinbelow. Intermediate the two tuning coil halves 7a and lb, and similarly intermediate the corresponding portions of the coils 8 and 9 there is mounted for rotation a tuning disc l3 which is continuously rotated on a shaft 14 by motor IS. The output of the circuit 5 may be utilized in any known manner such as in an audio device (not shown).

In order to obtain a more detailed picture of the invention reference may now be had to Figs. 2 and 3 wherein the tuning disc [3 is shown in side view in Fig. 2 and in a sectional view in Fig. 3. The disc l3 may comprise an insulating member l3a which may be composed of a suitable plastic or glass and preferably has mounted on one side thereof a foil of copper l6. This foil may take the form as shown in Fig. 2, that is, have a maximum expanse in width at its one end as at ii and gradually taper off toward a zero expanse at its other end 18, the rate of taper being determined by the scanning characteristic desired. The three coils i. 8 and 9 are preferably mounted in a circle about the axis of rotation 0r shaft M of the tuning disc l3 on a mechanical support or turret arrangement as indicated at IS. The turret l9 and with it the various coils may be rotated into the desired position so as to be brought into the main circuit. Each of the coils is provided with contacts 29, which are adapted to cooperate with stationary contacts 2| which form connections to the circuit 5.

In the sectional view of the device of Fig. 2 as seen in Fig. 3, it will be noticed by inspection that the disc I3 is disposed to rotate intermediate the two halves of the coil 9 which is the one that is connected to the main circuit through contacts 29 and 2 I.

The main circuit is terminated at the two stationary contacts 2| and each of the coils I, 8 and 9 may be rotated into the place assumed by coil 9 in Fig. 3 whereby a different portion of a given frequency band may be tunable by the circuit. The mechanical details of the rotatable turret l9 mounting the three coil sets has not been shown as many suitable arrangements are available. It will suffice to say that a simple device rotatable coaxially of shaft I4 is quite satisfactory. As a given set of coil portions isrotated into contact with the main circuit, the inductance of each respective coil is determined by the sum of the inductances of the two coil halves and twice the mutual inductance between the two coil portions.

Since however the tuning disc I3 is continuously rotated through the gap between the two coil portions, the factor of the total inductance depending on the mutual inductance of the two coil portions is varied in accordance with the width of the foil present in the gap at any one time. The foil in efiect acts as a shield between the coil portions whereby the mutual inductance is more or less reduced as the width of the foil is varied in the gap. The continuous variation in the expanse of the foil between the two coil portions results in a variation of the mutual inductance factor from a maximum to a minimum and consequently in a variation of the tuned resonance frequency of the circuit with time in accordance, for instance, with the saw-tooth variation shown in Fig. 4. Other relationships between frequency and time may, of course, be obtained by a suitable radial variation in the width of the foil.

It will be seen from the above, therefore, that I have provided a tunable circuit which may cover one or more sections of a given frequency band and the individual sections of which may be continuously scanned in respect to time.

Although I have shown the invention embodied in a receiving circuit it is of course understood that the invention may be equally well applied to other radiant energy translating circuits. Furthermore, while I have described above the principles of my invention in connection with specific scanning disc construction apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention.

I claim:

1. Frequency scanning means for use with the frequency tuning inductance of a tunable circuit comprising a rotatable non-conductive disc having a conductive portion including a copper foil arranged about the periphery of said disc and tapering in width from a maximum to a minimum.

2. A tunable circuit having connecting means, turret means mounting a plurality of circuit tuning inductances, each of said inductances having means for engaging said connecting means, said tunin inductances each comprising two halves, said turret being rotatable for selectively placing said respective inductances in connection with said circuit, and means for cyclically varying the inductance respectively connected to said circuit, said varying means comprising an electro-conductive member having a varying width rotatably disposed intermediate said two halves.

3. Apparatus as claimed in claim 2 in which said varying means comprises a rotatable nonconductive disc having a conductive portion including a metallic foil arranged about the periphery of said disc and tapering in width from a maximum to a minimum.

MARTIN SILVER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name- Date 1,432,455 Goldsmith Oct. 17, 1922 1,571,405 Goldsmith Feb. 2, 1926 1,983,380 Lynn Dec. 4, 1934 2,137,392 Cobb Nov. 22, 1938 2,141,613 Melicharek Dec. 27, 1938 FOREIGN PATENTS Number Country Date 202,115 Great Britain Aug. 16, 1923 586,036 France Mar. 13, 1925 

